[¹⁸F]FDG PET/CT in the Initial Staging and Restaging of Soft-Tissue or Bone Sarcoma in Patients with Negative or Equivocal Findings for Metastases or Limited Recurrence on Conventional Work-up: Results of a Prospective Multicenter Registry

The purpose of this study was to determine the impact of [¹⁸F]FDG PET/CT on the initial staging, restaging, clinical management, and outcomes of patients with soft-tissue and bone sarcomas. Methods: This single-arm, prospective multicenter registry enrolled 304 patients with 320 [¹⁸F]FDG PET/CT scans (November 2018 to October 2021). Eligibility included the initial staging of a grade 2 or higher or ungradable soft-tissue or bone sarcoma, with negative or equivocal findings for nodal or distant metastases on conventional imaging before curative-intent therapy, or restaging of patients with a history of treated sarcoma with a suspicion or confirmation of local recurrence or limited metastatic disease who were being considered for curative-intent or salvage therapy. The presence of local recurrence or metastases on [¹⁸F]FDG PET/CT was recorded. Clinical management after [¹⁸F]FDG PET/CT compared with pre-[¹⁸F]FDG PET/CT planned management and quantitative metabolic tumor parameters (SUV_max, metabolic tumor volume, total lesion glycolysis) were correlated with the outcome data for 171 patients. Results: At the initial staging, [¹⁸F]FDG PET/CT detected metastases in 17 of 105 patients (16.2%) with no metastases on conventional work-up and confirmed metastases in 44 of 92 patients (47.8%) with equivocal findings for metastases. At the time of restaging, [¹⁸F]FDG PET/CT detected local recurrence in 37 of 123 patients (30.1%) and distant metastases in 71 of 123 patients (57.7%). Overall, the change in treatment intent and treatment type was recorded in 64 of 171 cases (37.4%) and 56 of 171 cases (32.8%), respectively. The presence of metastases on [¹⁸F]FDG PET/CT was associated with shorter progression-free survival at the initial staging (P = 0.04) and shorter overall survival at the time of recurrence (P = 0.002). All quantitative metabolic tumor parameters correlated with progression-free survival and overall survival. Conclusion: [¹⁸F]FDG PET/CT frequently detects additional sites of disease compared with conventional imaging in patients with sarcomas that were being considered for curative-intent or salvage therapy. This increased detection impacts the clinical management in a third of patients referred for initial staging or presumed limited recurrence after primary therapy. The presence of metastases on [¹⁸F]FDG PET/CT is associated with poorer outcomes.